• Microchemical and Molecular Dating

      Currie, L. A.; Stafford, T. W.; Sheffield, A. E.; Klouda, G. A.; Wise, S. A.; Fletcher, R. A.; Donahue, Douglas J.; Jull, A. J. Timothy; Linick, T. W. (Department of Geosciences, The University of Arizona, 1989-01-01)
      The depth and reliability of archaeological and environmental information on ages, sources and pathways of carbon are being greatly enhanced through a new synergism between advances in "micro 14C dating" and advances in micro-organic analytical chemistry and individual particle characterization. Recent activities at the National Institute of Standards and Technology (NIST, formerly NBS) involving this linkage include dating individual amino acids isolated from bone collagen and the apportionment or tracing of individual carbon compounds derived from anthropogenic sources. Important knowledge has been gained through "direct" (sequential) and "indirect" (parallel) links between microchemistry and 14C measurement. The former is illustrated by 14C measurements on specific amino acids and on the polycyclic aromatic hydrocarbon (PAH) class of compounds. Isolation of the respective molecular fractions from far greater quantities of extraneous carbon held the key to valid dating and source apportionment respectively. Parallel data on 14C and molecular patterns promises new knowledge about the identity of sources of environmental carbon at the nanogram level through multivariate techniques such as principal component analysis and multiple linear regression. Examples are given for atmospheric particulate carbon, using PAM molecular patterns and laser microprobe mass spectral patterns.
    • Radiocarbon in Dissolved Organic and Inorganic Carbon from the Central North Pacific

      Druffel, Ellen R. M.; Williams, Peter M.; Robertson, Ken; Griffin, Sheila; Jull, A. J. Timothy; Donahue, Douglas J.; Toolin, Laurence J.; Linick, T. W. (Department of Geosciences, The University of Arizona, 1989-01-01)
      Radiocarbon measurements are reported for dissolved organic carbon (DOC) and inorganic carbon (DIC) from seawater samples collected from the Alcyone-5 cruise in the central North Pacific Ocean in 1985. Differences between the UV-radiation techniques used here and those reported by Williams, Oeschger and Kinney (1969) to oxidize and recover the DOC from sea water are presented. UV unoxldizable DOC in these samples is discussed in a separate publication (Druffel, Williams & Suzuki,1989). We briefly discuss the penetration of the bomb 14C signal into the DOC and DIC pools. The temporal variability of Delta-14C in DIC in surface samples taken every 2-3 days is presented. Concentrations of total dissolved free (FAA) plus combined (hydrolyzable) amino acids (THAA) and total dissolved carbohydrates (TCHO) measured in the same water samples are also reported. Our main aim is to present the chemical and isotopic data from samples collected during the Alcyone-5 cruise. Detailed interpretation is published elsewhere.
    • Spallogenic 14C in High-Altitude Rocks and in Antarctic Meteorites

      Jull, A. J. Timothy; Donahue, Douglas J.; Linick, T. W.; Wilson, G. C. (Department of Geosciences, The University of Arizona, 1989-01-01)
      14C in high-altitude rocks and in Antarctic meteorites of long terrestrial age has been found at levels consistent with in-situ production by cosmic rays. Levels of 0.2-0.59 dpm/kg (or 1.0-2.6 x 10^6 14C/g) are found in high-altitude samples ranging from 3300 to 5460m. Similar values are observed in Antarctic meteorites that have been dated by 81Kr by Freundel, Schultz & Reedy (1986) as over 100 kyr old.
    • The Recovery and Dating of Carbon Dioxide in Polar Ice Cores

      Wilson, A. T.; Donahue, Douglas J. (Department of Geosciences, The University of Arizona, 1989-01-01)
      A new method is described for recovering trapped CO2 from polar ice cores. The ice is sublimed under vacuum, and H2O vapor and CO2 are collected at appropriate cold traps. The application of this method to obtain CO2 from a specific ice core, the conversion of that CO2 to graphite, and the measurement of radiocarbon in the CO2 are described in detail. The potentialities and problems of the method are discussed.